Printing plate

ABSTRACT

A PRINTING PLATE IS CONSTITUTED A BASIC PLATE, A LAYER OF WATER INSOLUBLE HYDROPHILIC ACRYLATE OR METHACRYLATE POLYMERS OVER THE PLATE AND A PHOTO-SENSTIVE LAYER OVER THE LAYER.

y 15, 1973 SHUNJI TAKAISHI ET AL 3,733,200

PRINTING PLATE Filed Feb. 12 1971 INVENTORS flflu/vf/ 72/4449 Y 4 6424fiira United States Patent 3,733,200 PRINTING PLATE Shunji Takaishi,Tokyo, and Akira Kato, Yokohama, Japan, assignors to Hydron ChemicalCo., Ltd., Tokyo, and Kansai Paint Co., Osaka, Japan Filed Feb. 12,1971, Ser. No. 114,887 Claims priority, application Japan, Feb. 19,1970, 45/ 13,759 Int. Cl. G03c 1/94 US. Cl. 96-86 R 12 Claims ABSTRACTOF THE DISCLOSURE A printing plate is constituted a basic plate, a layerof water insoluble hydrophilic acrylate or methacrylate polymers overthe plate and a photo-sensitive layer over the layer.

The present invention relates to a printing plate. More particularly, itrelates to a printing plate having a photosensitive layer on the surfaceof water insoluble hydro philic acrylic resins layer.

The most conventional printing plates are aluminium plates having sandedor chemically treated surface on which e.g. gelatin, polyvinyl alcoholor albumins are applied together with one of photosensitive materialssuch as chromates and diazo compounds and finally those plates aredried, and exposed through a negative photo-film over the plate,developed and treated again. The photo-sensitively cured parts of linesand pictures absorb ink well due to the lipophilic property. On theother hand, the surface of the aluminium plate exposed by developingabsorbs water and repels ink. In the process of offset printing by usingsuch plates, the exposed surface of the aluminium plate gradually wearsthin by eternal friction together with cured parts and lines. In somecases, worn out lines and pictures are fixed and reinforced bylacquerlike materials. The surface of the aluminium plate, especiallyits sanded surface tends to wear out sometimes more easily than thephoto-sensitive cured layer. When the surface wears out, the defacedplate results in indistinct pictures with less hydrophilic function, andfinally it becomes impossible to print. Furthermore, water supply to thesanded aluminium surface has to be appropriate in order to obtain clearpictures and skilled work is required to the adjustment of water supply.

An object of the present invention is to provide a novel printing plate.

Another object of the present invention is to provide a printing platehaving an extremely great printing durability.

A further object of the present invention is to provide an improvedstarting printing plate bringing about a simplification of the make-upoperation.

Still further objects and entire scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

The printing plate according to the present invention comprises a basicplate, a layer of water insoluble hydro philic acrylate or methacrylatepolymers (hydrophilic acrylic resins) over the plate and aphoto-sensitive layer over the layer.

As a basic plate used in the starting printing plate of the presentinvention, there are employed metallic plates such as steel plate, tinplate, zinc plate, stainless steel plate, etc., plastic sheets such aspolyethylene terephthalate sheet, polystyrene sheet, acetyl cellulosesheet, hydrophilic acrylic resin sheets, etc. and papers.

It is indispensable that the hydrophilic acrylic resins which formhydrophilic layers are water insoluble. And the hydrophilic acrylicresins should be capable of absorbing at least 20% of its weight ofwater and preferably do not absorb more than about of its weight ofwater.

Preferably the hydrophilic monomer employed in the hydrophilic acrylicresins is a hydroxy lower alkyl acrylate or methacrylate or hydroxylower alkoxy lower alkyl acrylate or methacrylate, e.g. 2-hydroxyethylacrylate, 2- hydroxyethyl methacrylate, diethylene glycol monoacrylate,diethylene glycol monomethacrylate, 2-hydroxypropyl acrylate,2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropylmethacrylate, dipropylene glycol monomethacrylate and dipropylene glycolmonoacrylate. The most preferred monomers are the hydroxyalkyl acrylatesand methacrylates, particularly Z-hydroxyethyl methacrylate.

There can also be employed polymers of acrylamide, methacrylamide,N-alkyl substituted acrylamide and methacrylamide such asN-propylacrylamide, N -isopropyl acrylamide, N-isopropyl methacrylamide,N-propyl methacrylamide, N-butyl acrylamide, N-methyl acrylamide andN-methyl methacrylamide, diacetone acrylamide, N-(2-hydroxyethyl)acrylamide and N- (Z-hydroxyethyl) methacrylamide.

Likewise, there can be employed copolymers of these monomers with eachother or with other copolymerizable monomers. In fact, if thehydrophilic monomer gives a product which is water soluble, e.g.polyacrylamide, it is necessary to employ a copolymerizable monomer torender it only water swellable rather than water soluble. Thecopolymerizable monomer can be used in an amount of 0.05 to 50%.Preferably, comonomers include methyl acrylate, ethyl acrylate,isopropyl acrylate, propyl acrylate, butyl acrylate, sec. butylacrylate, pentyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate,ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butylmethacrylate, sec. butyl methacrylate, pentyl methacrylate, loweralkoxyethyl acrylates and methacrylates, e.g. methoxyethyl acrylate,methoxyethyl methacrylate, ethoxyethyl acrylate and ethoxyethylmethacrylate, triethylene glycol acrylate, triethylene glycolmethacrylate, glycerol monoacrylate and glycerol monomethacrylate.

There can also be used unsaturated amines, p-aminostyrene,oaminostyrene, 2-amino 4 vinyltoluene, alkylamino alkyl acrylates andmethacrylates, e.g. diethylaminoethyl acrylate, diethylaminoethylmethacrylate, dimethylaminoethyl acrylate, dimethylaminoethylmethacrylate, t-butylaminoethyl acrylate, t-butylaminoethylmethacrylate, piperidinoethyl acrylate, piperidinoethyl methacrylate,morpholinoethyl acrylate, morpholinoethyl methacrylate, 2-vinylpyridine,3-vinylpyridine, 4-viny1- pyridine, Z-ethyl-S-vinylpyridine,dimethylamino propyl acrylate, dimethylamino propyl methacrylate,dipropylaminoethyl acrylate, dipropylaminoethyl methacrylate.di-n-butylaminoethyl acrylate, di n butylaminoethyl methacrylate,di-sec. butylaminoethyl acrylate, di-sec. butylaminoethyl methacrylate,dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl sulfide,diethylaminoethyl vinyl ether, aminoethyl vinyl ether, aminoethyl vinylsulfide, monomethylaminoethyl vinyl sulfide, monomethyl aminoethyl vinylether, N-(gamma-monomethylamino) propyl acrylamide, N(betamonomethylamino) ethyl acrylamide, N- (beta-monomethylamino) ethylmethacrylamide, 10-amin0decyl vinyl ether, 8-aminooctyl vinyl ether,S-aminopentyl vinyl ether, 3-aminopropyl vinyl ether, 4aminobutyl vinylether, Z-aminobutyl vinyl ether, monoethylaminoethyl methacrylate,N-(3,5,5-trimethylhexyl) aminoethyl vinyl ether, N-cyclohexylaminoethylvinyl ether, 2-(1,1,3,3-tetramethylbutylamino) ethyl methacrylate,N-t-butylarninoethyl vinyl ether, N-methylamino-ethyl vinyl ether,N-Z-ethylhexylaminoethyl vinyl ether, N-t-butylaminoethylvinyl ether,N-t-octylaminoethyl vinyl ether, Z-pyrrolidinoethyl acrylate,2-pyrrolidinoethyl methacrylate, 3-dimethylaminoethyl)-2-hydroxypropylacrylate, 3- (dimethylaminoethyl -2-hydroxypropyl methacylate,Z-aminoethyl acrylate, 2-aminoethyl methacrylate. The presentlypreferred amino compounds are alkylaminoethyl acrylates andmethacrylates, most preferably t-butyl aminoethyl methacrylate.

Preferably, the cross-linking agent is present in an amount of 0.1 to2.5%, most preferably not over 2.0%, although from 0.05 to 15% or even20%, of crosslinking agents can be used. Of course, care should be takenthat cross-linking agents are not used in an amount which renders theproduct incapable of absorbing at least 20% of water.

Typical examples of cross-linking agents include ethylene glycoldiacrylate, ethylene glycol dimethacrylate, 1,2- butylene glycoldimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycoldimethacrylate, propyl ene glycol diacrylate, propylene glycoldimethacrylate, diethylene glycol dimethacrylate, di-propylene glycoldimethacrylate, diethylene glycol diacrylate, dipropylene glycoldiacrylate, divinyl benzene, divinyl toluene, diallyl tartarate, allylpyruvate, allyl maleate, divinyl tartrate, triallyl melamine, N,N'methylene bis acrylamide, .glycerine trimethacrylate, diallyl maleate,divinyl ether, diallyl monoethylene glycol citrate, ethylene glycolvinyl allyl citrate, allyl vinyl maleate, diallyl itaconate, ethyleneglycol diester of itaconic acid, divinyl sulfone,h'exahydro-1,3,5-triacryltriazine, triallyl phosphite, diallyl ester ofbenzene phosphonic acid, polyester of maleic anhydride with triethyleneglycol, polyallyl glucose, e.g. triallyl glucose, polyallyl sucrose,e.g. pentaallyl sucrose, sucrose diacrylate, glucose dimethacrylate,pentaerythritol tetraacrylate, sorbitol dimethacrylate, diallylaconitate, divinyl citraconate, diallyl fumarate.

There can be included ethylenically unsaturated acids or salts thereofsuch as acrylic acid, cinnamic acid, crotonic acid, methacrylic acid,itaconic acid, aconitic acid, maleic acid, fumaric acid, mesaconic acidand citraconic acid. Also, as previously indicated there can be usedpartial esters such as mono 2-hydroxypropyl itaconate, mono2-hydroxyethyl itaconate, mono Z-hydroxyethyl citraconate, mono2-hydroxypropyl aconitate, mono 2-hydroxyethyl maleate, mono2-hydroxypropyl fumarate, monomethyl itaconate, monoethyl itaconate,mono methyl Cellosolve ester of itaconic acid (methyl Cellosolve is themonomethyl ether of diethylene glycol), mono methyl Cellosolve ester ofmaleic acid.

The polymers can be prepared as casting syrups, as aqueous dispersions,by aqueous suspension polymerization or as solutions in organic solventssuch as ethyl alcohol, methyl alcohol, propyl alcohol, isopropylalcohol, formamide, dimethyl sulfoxide or other appropriate solvent.

Polymerization can be carried out at 20 to 150 C., frequently 35 to 90C. and can be completed after applying. The polymerization can becarried out employing a free radical catalyst in the range of 0.05 to 1%of the polymerizable monomers. Typical catalyst include tbutylperoctoate, benozyl peroxide, isopropyl percarbonate,2,4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumenehydroperoxide and dicumyl peroxide. Irradiation, e.g. by ultravioletlight or gamma rays, also can be employed to catalyze thepolymerization.

The hydrophilic polymer is used as a solution, as a casting syrup or asa sheet, coated on the surface of basic plate by means of painting,casting, adhering and the like with or without using adhesives, andforms a water insoluble hydrophilic resin layer. The thickness of thehydrophilic resin layer is generally 5 to 300 microns, preferably 10 to50 microns. Thus, by providing a water insoluble hydrophilic layer onthe suface of the basic plate, there can be attained good results inrespect of dimension stability of the hydrophilic layer or printingplate, its installation on the printing machine and the like. As thehydrophilic resin is transparent, when a transparent plastic sheet isused as a basic plate, it becomes wholly transparent. Therefore, it isvery advantageous, because the registering at the multi color printingis easier.

Further, there can be incorporated with the hydrophilic resin to providea layer having increased mechanical strength as well as adherence to thebasic plate by oxidizing type curing agents such as sodium, potassium orammonium chromate or dichromate, aminoplast resins such as melamineresin, benzoguanamine resin or acetoguanamine resin, acid anhydridessuch as maleic anhydride, citraconic anhydride, succinic anhydride,phthalic anhydride, trimellitic anhydride, pyromellitic anhydride andthe like, polyamines such as ethylene diamine, propylene diamine,diethylene triamine, tetraethylene pentamine, piperazine, m-xylylenediamine, p-xylylene diamine, m-phenylene diamine, p-phenylene diamine,benzidine, diaminodiphenyl methane, diaminodiphenyl sulfone,3,3-dichloro-4,4-diphenyl methane diamine, naphthalene diamine and thelike. The amount of the curing agents to the hydrophilic resin isgenerally less than 2% by weight, preferably 0.1 to 0.5% by weight.

However, mechanical strength of the hydrophilic resin layer increases byaddition of the curing agents, while the hydrophilic property sometimesdecreases. In such a case, it is preferable to add fine divided powderedmaterials to the hydrophilic resin. By such addition sufficienthydrophilic property for a printing plate is attained. As such powderedmaterials, there are fine divided powdered inorganic materials such as,e.g., silica, alumina, magnesia, zirconia, barium sulfate, acidactinated clay, talc and diatomaceous earth. Preferable materials aresilica and alumina. The amount of the powdered materials to thehydrophilic resin is less than 5% by weight, preferably 0.5 to 2% byweight.

As the compound which forms a photo-sensitive layer according to thepresent invention, there are used photocurable compositions composed ofvinyl monomers, photosensitizers and resins such as unsaturatedpolyester resin, alkyd resin, acrylurethane resin, silicone modifiedacrylic resin, polybutadiene and cellulose; light-sensitive polymersmodified by compounds such as diazo compounds, azide compounds, organosulfur compounds and cinnamic acid compounds; and compositions composedof dichromates and gelatin, polyvinyl alcohol or albumin. Consideringthe printing capacity and resolving power, acrylurethane resin isespecially superior to the others.

The above mentioned polymeric materials are dissolved in organicsolvents having the property of swelling or partially dissolving thehydrophilic layer, e.g., alcohols, ketones and esters, and are appliedto the surface of the hydrophilic resin layer by coating and drying. Insuch a case, the surface of the hydrophilic resin layer swells orpartially dissolves and mixes with photo-sensitive compounds, and bothlayers are adhered together. Thus obtained printing plate is exposedusing a negative film over it, developed, washed by water and dried, andif necessary absorbed in water. Then it is equipped to the otfsetprinting machine and used in the offset printing. It gives us excellentresults. When the hydrophilic layer is relatively thicker, water supplyby fountain roller may be extremely little.

In the present invention, we use a water insoluble hydrophilic resincoated metallic plate, plastic sheet, paper and the like instead of theconventional aluminium plate. Therefore, if abrasion of the hydrophilicresin layer occurs, lithographic printability is not completelyprevented where the hydrophilic layer exists. Thus printing capacity andits durability is greatly increased. For example, though we could onlyprint less than 20,000 sheets of paper by using the conventionalaluminium plate, which had been sanded and then coated with albumin, itis a surprising effect that We can print more than 100,000 sheets ofpaper by using the printing plate according to the present invention.

Further effect of the present invention is that only a little supply ofwater is sufiicient for the lithographic printing. That is to say, thehydrophilic resin layer which absorbed water releases water slowly andconstantly, and it is possible to print with only a little water supply.Thus no excessive water is transferred to the printing paper andprinting precision increases remarkably without any stretch in the sizeof paper. These features also contribute to make the printing operationeasy as no skilled control is required in the water supply.

As mentionad above, the printing palte having a photosensitive layer onthe hydrophilic resin layer has very excellent advantages in comparisonwith a conventional printing plate having a photo-sensitive layer on thealuminium plate directly, and is very useful in respect to increasingprinting durability and printing precision, and bringing about simpleprinting operation.

The invention will be understood best in connection with drawingwherein:

FIG. 1 shows a partial sectional view of the printing plate according tothe invention; and

FIG. 2 shows a partial sectional view of the printing plate afterexposing and developing.

Referring more specifically to the drawing, the starting printing plateis constituted of a basic plate 1, a layer 2 of water insolublehydrophilic acrylic resins over the plate 1 and a photo-sensitive layer3 over the layer 2. The thickness of the layers 2 and 3 are greatlyexaggerated for illustrative purposes.

Unless otherwise indicated in the specification and claims all parts andpercentages are by weight.

EXAMPLE 1 400 parts of polyethyleneglycol-400 Was added to 360 parts oftolylene diisocyanates, reacted by heating at a temperature of 140 C.for 30 minutes and cooled, then there were added 260 parts of2-hydroxyethyl methacrylate and 0.21 part of p-benzoquinone to thereactant and reacted at a temperature of 40 C. for 24 hours to obtainthe unsaturated acrylurethane resin (I). The resin (I), was a veryviscous liquid at room temperature. The photosensitive resin compositionwas obtained by mixing 50 parts of resin (I) with 50 parts of commercialcellulose phthalate, 1 part of benzoin ethylether and 100 parts ofacetone.

EXAMPLE 2 The solution consisting of 2-hydroxyethyl methacrylate 79.6%,ethyleneglycol dimethacrylate 0.3%, glycerol 20% and diethylpercarbonate 0.1% was poured into the space between two glass platesadjusted by spacer in order to maintain 0.15 mm. of space carefully soas to not form bubbles. The composition was polymerized maintaining atemperature of 65 C. for 20 minutes, then the transparent sheet obtainedby removing the plates was washed by distilled water and the glycerolextracted out, and further dried at a room of 40% of relative humidityat a temperature of 25 C. for 24 hours to obtain a hydrophilic resinsheet. The sheet was adhered to the aluminium plate having 0.15 mm. ofthickness using epoxy resin polyamide resin mixed adhesive. The otherside of the resin sheet was coated uniformly with photo-sensitive resincomposition obtained in Example 1 so that the thickness of drying filmwas about 2 microns, and dried to obtain the printing plate.

After the negative film was put on the printing plate,

6 the plate was set in the vacuum printing frame and exposed by a highpressure mercury lamp at a distance of 35 cm. for one minute, then itwas developed by 1% ethanolamine aqueous solution, washed by water anddried to obtain the lithography for printing. Otfset printing wascarried out by using the lithography, and very excellent printingeffects having good distinction and measure accuracy were obtained. Alsoit was able to print more than 100,000 sheets of paper per plate, andthe control of water supply was easier than that with the conventionalmethod.

EXAMPLE 3 Hydrophilic monomer solution of Example 2 was coated on thealuminium plate having 0.15 mm. of thickness which was previously coatedwith epoxy resin-polyamide resin mixed primer so as to be 10 micronsthickness, so that the thickness of the hydrophilic resin was about 0.2mm, and polymerized under nitrogen atmosphere by similar condition asExample 2. Then the photography for printing was prepared and offsetprinting was carried out, similar good results as Example 2 wereobtained.

EXAMPLE 4 A hydrophilic resin sheet obtained by Example 2 was adhered onthe surface of polyethylene terephthalate sheet having 0.2 mm. ofthickness by means of epoxy adhesive and the other surface of the resinsheet was coated with diazo compound Fuji Super-Resist: trademark of(Fuji Chemicals Co., Ltd.) as thin as 3 microns, exposed throughnegative fihn and treated as prescribed to obtain a printing plate.Offset printing with four colors was carried out using the printingplate, and the good results of Example 2 were obtained. Also registeringof each plate was carried out easily and rapidly, because of itstransparency.

EXAMPLE 5 1,000 grams of xylene, grams of 2-hydroxyethyl methacrylateand 0.33 gram of isopropyl percarbonate were charged to a flask equippedwith an agitator and heating mantle. The flask was rapidly agitated at100 C. under a nitrogen atmosphere. After 15 minutes the slurry wasfiltered hot to isolate the polymer. The polymer powder was reslurriedin 300 ml. of xylene, filtered and dried. A 98% yield of 2 to 5 micronparticle size alcohol soluble powder was obtained. 100 grams of thepolymer powder was dissolved in 200 ml. of methanol, then added 0.2 gramof epoxy resin and 1.5 grams of fine divided silica powder and dispersedhomogeneously. The thus obtained solution was coated on epoxyresin-polyamide resin mixed primer coating which was previously coatedon a steel plate having a 0.15 mm. thickness so as to be 10 micronsthick so that the dried thickness of layer was 20 microns and dried.Then the lithography for printing was prepared and offset printing wascarried out, similar good results to those in Example 2 were obtained.Mechanical strength of the hydrophilic resin layer was good.

EXAMPLE 6 EXAMPLE 7 A casting syrup was made from 100 grams of2-hydroxyethyl methacrylate, 0.2 gram of ethyleneglycol dimethacrylateand 0.4 gram of t-butyl peroctoate. 0.2 gram of potassium dichromate and2 grams of fine divided silica powder were added into the syrup anddispersed homogeneously. The syrup was coated on an aluminium plate sothat the dried thickness was 25 microns. Then the lithography forprinting was prepared and offset printing was carried out, similar goodresults to those of Example 2 were obtained. Mechanical strength of thehydrophilic resin layer was very good.

EXAMPLE 8 7.5 liters of ethanol, 100 grams of t-butylaminoethylmethacrylate, 150 grams of N-isopropyl acrylamide and 2.25 kilo-grams of2-hydroxyethyl methacrylate (containing 0.3% of ethyleneglycoldimethacrylate) together with 10 grams of t-butyl peroctoate werecharged into a vessel and the solution heated at 85 C. for 7 hours toeffect polymerization to a 90% conversion level. 0.25 gram of maleicanhydride and 1 gram of fine divided silica powder were added into thepolymer solution thus obtained, and dispersed homogeneously. Thesolution was coated on an aluminium plate so that the dried thicknesswas 35 microns. Then the lithography for printing was prepared andoffset printing was carried out, similar good results to those inExample 2 were obtained. Mechanical strength of the hydrophilic resinlayer was very good.

What is claimed is:

1. A printing plate comprising a basic plate, a layer of water insolublehydrophilic acrylate or methacrylate polymer selected from the groupconsisting of a polymer of a hydrophilic hydroxy lower alkyl acrylate,hydroxy lower alkyl methacrylate, hydroxy lower alkoxy lower alkylacrylate and hydroxy lower alkoxy lower alkyl methacrylate over saidplate and a photosensitive layer over said hydrophilic polymer layer.

2. A printing plate according to claim 1 wherein the Water insolublepolymer comprises a polymer selected from the group consisting of apolymer of hydroxyethyl acrylate, hydroxyethyl methacrylate,hydroxypropyl acrylate and hydroxypropyl methacrylate.

3. A printing plate according to claim 2 wherein the polymer is a linearpolymer.

4. A printing plate according to claim 3 wherein the polymer is ahomopolymer.

5. A printing plate according to claim 2 wherein the polymer is acopolymer of said acrylate or methacrylate with a minor amount up to 15%of a cross-linking agent.

6. A printing plate according to claim 1 wherein the water insolublehydrophilic polymer layer includes a curing agent in an amount up to 2%by weight.

7 A printing plate according to claim 6 wherein the water insolublehydrophilic polymer layer includes finely divided powdered inorganicmaterial.

8. A printing plate according to claim 7 wherein the Water insolublepolymer comprises a polymer selected from the group consisting of apolymer of hydroxyethyl acrylate, hydroxyethyl methacrylate,hydroxypropyl acrylate and hydroxypropyl methacrylate.

9. A printing plate according to claim 8 wherein the polymer is a linearpolymer.

10. A printing plate according to claim 8 wherein the polymer is acopolymer of said acrylate or methacrylate with a minor amount up to 15of a cross-linking agent.

11. A printing plate according to claim 7 wherein the fine dividedpowdered inorganic material is powdered silica.

12. A printing plate according to claim 7 wherein the fine dividedpowdered inorganic material is powdered alumina.

References Cited UNITED STATES PATENTS 2,930,317 3/1960 Perkins 1014623,055,295 9/1962 Perkins 101462 3,173,787 3/1965 Clement et a1. 9685 X3,338,164 8/1967 Webers 101-457 3,298,852 1/1967 Beatty et a1. 9633 X3,440,047 4/1969 Levinos et al. 9686 X 3,600,166 *8/ l97l Sieg et a19686 X DAVID KLEIN, Primary Examiner US. Cl. X.R.

